Hi, I made a sensor breakout for the EK ISC Connector (J27) and enabled the relevant kernel options (following this guide: https://www.at91.com/linux4sam/bin/view ... M/UsingISC) and I added a dtsi for the sensor (based on at91-sama5d2_xplained_ov7740.dtsi).
The sensor seems to be detected at the right I2C address (0x5C), however when running v4l2-ctl --all (or v4l2grab) the image width and height are both set to 0. Can someone please explain what I'm missing or how to debug this further ? Thanks!

That seems to be an understatement, as you seem to have shown nothing that indicates positive communication with the sensor device.
Recheck all of your connections.
Review the system log for salient isc, i2c, and mt9v034 driver messages.
If necessary:
(a) Enable debug for the pinctrl subsystem (via menuconfig) to verify pin assignments.
(b) Insert printk()s to the probe() and register() routines of mt9v034.c to verify driver installation.

I finally managed to get an image from the sensor after fixing the dts (see the notes) and initializing the try crop struct in this function mt9v032_set_format() to any fixed values. Note this function is called from atmel_isc.c with a different v4l2_subdev_pad_config than the one passed to (and initialized in) mt9v032_open() so the try crop->width and crop->height are both set to 0 which in turn sets format->width and format->height to 0. I added some printk's to mt9v032_set_format() and this is the output: